This invention relates to an optical scanning system which provides bi-directional scan capabilities in a simplex and dulplex mode of operation.
It is known in the prior copying art to provide document handling systems in conjunction with duplex copying capabilities. U.S. Pat. No. 4,111,547 describes various types of duplex copying modes. In duplex/duplex copying, both sides of the ducument sheet are copied onto both sides of a copy sheet. In duplex/simplex copying, both sides of the ducument with images on both sides are copied onto one side of two successive copy sheets. In simplex/duplex copying, one side of two successive documents are placed on opposite sides of a copy sheet. The present invention is directed towards a scanning system which is particularly suited for a simplex/duplex copying mode.
A common problem in prior art systems which use a document scanning mechanism in conjunction with a through lens and a simplex/duplex mode is that the originals to be copied in the landscape mode (short edge feed) have the second side copied upside down when introduced into the illumination/exposure area on the platen in the same orientation. In a typical prior art system in which such a short edge fed document is scanned from left to right and an image projected through a lens onto the photoreceptor surface, in order for the developed latent images of successive documents to be transferred and formed right side up on both sides of the copy sheet, the second document to be copied must be oriented in a direction opposite to the first document. Stated another way, the reversion of every other original is required in a simplex/duplex copying mode, reversion defined as rotating the document 180.degree. in its plane, end to end. This reversion has been accomplished in the prior art either manually or by a semi-automatic mechanism, for example, of the type described in Xerox Disclosure Journal Publication "Separation and Sequencing to Achieve Reversion", Volume 10, Number 1, published Jan. /Feb. 1985. It would be desirable to feed all input documents into an exposure station with the input documents having the same orientation. The present invention is, therefore, directed to an optical system which accomplishes reversion utilizing a unique optical scanning system. More particularly, the invention is directed toward a bi-directional scanning system for enabling a duplex copying for original documents including; means for automatically conveying original documents in like orientation, onto an object plane; optical scanning means for incrementally illuminating said object in a first and second direction, and first and second projection lenses associated with said first and second scan direction, said lenses introduced onto the optical path coincide with the initiation of the associated scan cycle.
The invention can also be used to copy landscape oriented documents in a long edge feed mode so as to increase throughput or decrease paper path length.